The next time I see someone saying XML is inevitably hard to program to, I'll have a link to some code to show them:

public static void main(String[] args) {
  Abdera abdera = new Abdera();
  abdera.getFactory().registerExtension(new ActivityExtensionFactory());
  abdera.getFactory().registerExtension(new AtomMediaExtensionFactory());

  Feed feed = abdera.newFeed();               
  ActivityEntry entry = new ActivityEntry(feed.addEntry());
  entry.setId("tag:site.org,2009-01-01:/some/unique/id");
  entry.setTitle("pt took a Picture!");
  entry.setVerb(Verb.POST, false);
  entry.setPublished(new Date());
  Photo photo = entry.addTypedObject(ObjectType.PHOTO);
  photo.addThumbnail(
    "https://example.org/pt/1/thumbnail",
    "image/jpeg", 16, 32);
  photo.addLargerImage(
    "http://example.org/ot/1/larger",
    "image/jpeg", 1024, 768);
  photo.setTitle("My backyard!");
  photo.setDescription("this is an excellent shot.");
  photo.setPageLink("http://example.org/pt/1");
}

That generates Activity Streams (AS), an extension to Atom - you can read about it here - http://activitystrea.ms. I think Activity Streams are going to be an important data platform for social networking.